Quality Improvement Initiatives for the Embankment and Concrete Surface Water-Shielding Slab of the Nanma Dam (Concrete Face Rockfill Dam)

Abstract

Nanma Dam is a concrete face rockfill dam constructed by the Water Resources Agency in Kanuma City, Tochigi Prefecture. This report describes the quality improvement initiatives implemented in the embankment construction and the concrete face slab works. For rock material selection, on-site measurement techniques such as the echo tip and magnetic susceptibility meters were used, along with a drilling energy classification system. Automated bulldozers and vibration rollers were applied for compaction, and various quality control systems were adopted. In the face slab construction, a concrete mix design that ensures long-term slump retention and minimizes segregation was developed, and slipform performance was verified through trial placements. These efforts successfully enhanced both construction quality and efficiency.